Methods of reconstructing soft tissues are needed for patients that suffer from disease states that implicate those tissues, or patients who have undergone surgery, including surgery to correct certain disease states.
For example, approximately 400 million people worldwide were reportedly affected by bladder disease by the end of 1999. One of the common forms of bladder cancer is urinary bladder cancer. This cancer is also a common malignancy of the genitourinary tract and a leading cause of cancer among American men. Many forms of bladder cancer are superficial. In the majority of these cases, a suitable treatment involves local resection of the cancerous portion of the bladder wall combined with adjuvant intravesical immuno-chemotherapy. However, in cases where this treatment regimen is unsuccessful, and in cases where the bladder cancer is not superficial, treatment often involves cystectomy of a portion of, or of the entire, bladder wall. This procedure is performed in order to stop the progression of the disease and to reduce mortality. Following such resection procedures, the bladder can be reconstructed using implants.
The bladder is a musculomembraneous sac that acts as a reservoir for urine. The bladder is constructed from two main parts: (a) the body, which is the major part of the bladder and the portion in which urine collects; and (b) the neck, which is a funnel-shaped extension of the body, passing into the urogenital triangle (trigone), and connecting with the lower bladder opening (urethra). Two ureters, originating at the kidneys, enter the bladder at the uppermost angles of the trigone. An empty bladder has the form of a flattened tetrahedron, with its vertex tilted forward, thus presenting structures such as a fundus, a vertex, and superior and interior surfaces. A full bladder contains about 0.5 liters (L) of fluid and assumes an oval form, the long diameter of which is about 12 cm in length.
Bladder tissue is composed of four coats, a serous, a mucous, a submucous, and a muscular coat. Each of these coats is also associated with an extracellular matrix. The serous coat is a very thin layer derived from the peritoneum, a transparent membrane that lines the abdominal cavity in mammals. It develops the superior surface and the upper parts of the lateral surfaces of the bladder wall. The mucous coat is thin and smooth, and has a loose texture allowing it to be arranged in folds when the bladder is empty. However, over the trigone, the mucous membrane is formed from different-shaped urothelial cells that can accommodate both the distended and the contracted bladder. The submucous coat is formed from a layer of interstitial tissue, which is closely attached to the mucous coat and connects it to the muscular coat. The muscular coat is the major component of the bladder wall and is formed from three layers muscular fibers, an external layer, a middle layer, and an inner layer.
The external layer of muscular fibers has a longitudinal arrangement. These fibers are thick as compared to the other layers in the muscular coat of the bladder wall. The middle layer of muscular fibers has a circular arrangement. These fibers are generally thin, and scattered irregularly over the body of the bladder. The inner layer of muscular fibers, that next to the submucous coat, has a general longitudinal arrangement, and are also arranged in a thin manner.
It is desirable that the material from which implants are constructed or fabricated exhibit similar material and mechanical properties to the native tissue being replaced or reinforced. Accordingly, materials that mimic soft tissues, such as bladder tissue described herein, are desirable.